"A History of Western Music" 5th edition, chapters 1,2,3."
Groves
New Dictionary of Musicians "modes and scales section."
A General History of Music From The Earliest
Ages To The Present
"History of the Church Modes" by
Larry Mysz
The Melodic Minor was created to smooth out the vocal lines in choir music, as the Aug 2nd was not pleasant for vocal arrangements. I think it was Mozart who spear headed that effort. All variations of the minor scale are useful, and can actually help in chromatic usage. I like using the Hungarian minor allot as well as all Aolian based scales, but not all scales can be KING.